Over the past two decades, treatment of diseases by the transluminal placement of a prosthesis has garnered increasing attention. In the field of vascular disease, this therapeutic modality now represents the intervention of choice for most occlusive lesions. The satisfactory results obtained with this treatment strategy has encouraged its application for the management of lesions such as aneurysms which are characterized by partial or complete loss of structural integrity rather than hindrance to blood flow. Beginning with U.S. Pat. No. 4,140,126, multiple prostheses have been described for the purpose, some of which the stage of clinical trial. Experience with these prostheses has demonstrated that while they do have therapeutic value, all suffer from a common drawback. They are too bulky to be implanted without creating a surgical vascular access, thereby negating one of the major advantages of the transluminal approach. This characteristic also make them difficult to implant in patients with tortuous blood vessels. Another limitation associated with the use of these prostheses is the inability to treat lesions involving the craniocerebral or visceral branches of the aorta. That the prostheses in use have the same disadvantage is not a coincidence because all are based on the same underlying design: a flexible non-porous tube braced by an expandable metallic skeleton. Reducing the metallic skeleton to a single, sturdy metallic collar has been proposed as one way to reduce the bulk of a prostheses during introduction (PCT International Application WO 97/48350). While this modification certainly makes for a more streamlined device, it does not eliminate the need for surgically creating a vascular access because the introducer catheter required has an outer diameter of is approximately 5 mm (15 Fr). Furthermore, clinical experience indicates that the absence of support along the longitudinal axis of the device is likely to increase the risk of complications associated with its use such as migration (Resch T. et. al. J Vasc Interv Radiol 1999; 10:257–64).
Deployment of the tubular component of the prosthesis and its metallic skeleton in sequence suggests itself as a possible solution to the problem. A retrievable prosthesis comprising a flexible polymer tube provided with two encircling resilient loops for temporary fixation attached independently to two metals leads during implantation is the subject of U.S. Pat. No. 5,776,186. The inherent resistance of a resilient loop to deformation limits the degree to which the prosthesis can be compacted during delivery into the arterial system. Besides, the presence of two manipulation leads running along the length of the prosthesis and the relatively complex and bulky mechanism for attaching them to the prosthesis, and the presence of the mechanism radially adjacent to the prosthesis further increases the profile of the device making it necessary for the introducer catheter to be at least 12 Fr in size (OD≈3.8 mm). This requirement mandates the surgical opening of a blood vessel for placement of the prosthesis. The prosthesis also lacks any intrinsic longitudinal support once the manipulation leads are withdrawn following implantation, detracting from its potential safety profile (Resch T. et. al. J Vasc Interv Radiol 1999; 10:257–64). Furthermore, in common with currently available prostheses, it cannot be used for treating aortic disease involving the craniocerebral, visceral, or renal branches. Perhaps for these reasons no reports about the use even in animal models has been published thus far in medical literature. Kerr described a conceptually similar prosthesis comprising a polymer tube supported by two bent guidewires each of which is bent to define a loop (U.S. Pat. No. 6,015,422). After the tube is deployed in the blood vessel and a stent coaxially implanted to anchor it, an expandable device such as an angioplasty catheter is used to break the loops allowing the guidewires to be withdrawn. As the prosthesis is not physically attached to the guidewires, the possibility exists of inadvertent separation of the prosthesis from the latter from the latter during delivery. Further in common with the invention covered U.S. Pat. No. 5,776,186, and cited above, the resilient loops limit the degree to which the prosthesis can be compacted during delivery into the target organ. In an alternative embodiment two guidewires are provided which are bent to form two outwardly-biased tines that are attached to the prosthesis with threads. Expanding the prosthesis with a device such as an angioplasty catheter tears the threads allowing the withdrawal of the guidewires. On the basis of published data, neither does this embodiment promise a materially more streamlined profile during delivery, as the introducer catheter 12.9 Fr (O.D.≈4.1 mm) in calibre is required for deployment (Kerr A. J Vasc Interv Radiol 1999; 10:281–4). The mechanism used for detaching the prosthesis carries the risk of damaging the prosthesis. Furthermore the prosthesis is not suitable for treating aortic disease involving the craniocerebral, visceral, or renal branches.
Thus there exists a need for a prosthesis for transluminal implantation that has a low enough profile to be introduced into the body by the non-surgical, percutaneous, approach and yet has sufficient longitudinal rigidity to minimise the risk of complications. In addition the prosthesis should be suitable for treating vascular lesions involving the aorta and its craniocerebral, visceral, or renal branches. These requirements are fulfilled by the invention under consideration.